This invention relates to an orbit vehicle launch system and relates in particular to the utilization of a plurality of reusable turbojet propelled booster vehicles with fly back capability to provide horizontal takeoff and efficient ascent of the orbit vehicle to staging altitude and speeds, with both orbiter and booster wings providing lift during takeoff and ascent.
Projections for earth orbiting solar power collecting stations and industrial processing plants indicate the need for frequent space flights. The current concept for accomplishing these flights, the space shuttle concept, is the use of refurbishable solid rocket boosters and an oxygen/hydrogen rocket propelled orbiter vehicle for the launch of large payloads to earth orbit. The orbiter vehicle, carrying a payload of approximately 65,000 pounds mass (65K lb.sub.m), is mounted piggyback fashion to a large expendable hydrogen fuel tank which has refurbishable solid rocket boosters attached on the sides. The space shuttle system is designed for vertical takeoff (VTO) under the booster rocket power. At staging altitude, the booster rockets drop from the hydrogen fuel tank and fall to earth, landing in the ocean to be recovered later for refurbishing. The orbiter and tank continue ascending to orbit altitude under oxygen/hydrogen rocket power. The oxygen and hydrogen propellant tanks are discarded at orbit altitude. The orbiter retains enough propellant to enter circular orbit and to jetison from orbit and glide to a horizontal earth landing.
The mission scenario shows that the current space shuttle's high launch costs must be reduced by an order of magnitude before large scale space utilization can become a practical goal. The dominant factors contributing to the high space launch costs are the replacement of expendable propellant tanks and the recovery, refurbishment, and refueling of the solid rocket motors. A variety of space transportation systems have been studied which avoid these recurring costs. However, several factors such as high technical risk, high development costs, and lack of versatility of horizontal takeoff capability, have precluded commitment to any particular system to date. None of the previous systems simultaneously satisfy the low cost and versatility goals. To provide a comparative basis to assess the present invention, a brief review of the various space transportation systems studied to date is warranted.
Several concepts of fully reusable vehicles with the versatility of horizontal takeoff (HTO) from runways have been studied. One concept, the aerospace plane, requires a very low and presently unobtainable structural mass fraction, scramjet propulsion, and complex air collection equipment. A second reusable HTO vehicle concept, the air breathing launch vehicle (ABLV) uses turbojets, ramjets, and scramjets with hydrogen fuel in the booster, which separates at a Mach number of approximately 10. Consequently, the first stage is larger than the orbiter. Furthermore, the high speed and advanced propulsion systems of the launch vehicle requires advanced technology with its associated high costs. A third reusable HTO concept, studied in several variations from the late fifties into the seventies, employs a large subsonic or supersonic carrier aircraft (usually designed for other missions) as a first stage. This large and complex booster stage would be very expensive. Therefore, the three reusable HTO vehicl concepts of the prior art satisfy the versatility goals but not the low cost goals.
More recent space transportation concepts studied, that avoid recurring costs of the space shuttle, include the single stage-to-orbit (SSTO) concepts. Most SSTO concepts are designed for vertical takeoff (VTO); one known concept is designed for horizontal takeoff from a rocket powered sled. The VTO concepts employ advanced rocket engines using both hydrocarbon and hydrogen fuel. An all hydrogen fueled VTO vehicle designed to carry the same payload as the current space shuttle, 65K lb.sub.m, would have a relatively high gross weight of 3.6M lb.sub.m. The sled launched HTO concept has been proposed to enable use of hydrogen fuel only (by use of a two position nozzle added to the current space shuttle main rocket engines (SSME) at considerably less gross weight than the all hydrogen VTO concept. But a sled offers limited takeoff azimuths and few launch sites, thus limiting operational versatility. Neither the VTO nor the sled launched HTO operational modes offer the convenience of a conventional runway takeoff mode. Thus, the single stage-to-orbit concepts may satisfy cost objectives but lack versatility.
The present invention employs current engine and structural technology to provide fully reusable horizontal takeoff space transport that has potentially low initial and operating costs. This potential stems from the use of small reusable turbojet propelled, winged booster vehicles instead of space shuttle type solid rocket boosters, or large ABLV or carrier aircraft boosters discussed above. The present invention introduces a new concept in orbiter launch systems, called "parallel lift", which enables the utilization of the small boosters. In the parallel lift system, both orbiter and booster wings provide lift during takeoff and climb with the orbiter wings providing approximately 70-75 percent of the total lift. This permits the booster to be reduced by approximately one-third in size and weight compared to a booster providing the entire lift during takeoff and climb. The orbiter wing is sized primarily to withstand re-entry heating. The booster wing is sized for flyback and landing, but is modified to better match the orbiter wing for takeoff.
Furthermore, for a given payload a lighter and less expensive orbiter vehicle can be used than is feasible with the advanced technology SSTO concepts. For 65K lb.sub.m payload, two booster vehicles, with fuel, have a combined weight of only 0.8M lb.sub.m and the total launch vehicle weight is 2.6M lb.sub.m, about half that of current space shuttle.
In addition, this space transport concept offers the potential operational versatility of lateral offset orbit insertion, ferrying capability, intact abort and recall landing and versatility in takeoff location, which in combination may enable round trips to space from many existing airfields.
An object of the present invention is to provide a current technology low cost and versatile orbiter launch system.
A further object of the present invention is to provide a launch system which yields the foregoing advantages and utilizes small turbojet powered, winged booster vehicles releasably connected to the orbiter vehicle, and which utilizes parallel lift during takeoff and ascent to staging.
A further object of the present invention is to provide a launch system offering operation versatility of offset orbit insertion, ferrying capability, intact abort and recall landing and horizontal takeoff.
Other objects and advantages of the present invention will be readily apparent from the following description and drawings which illustrate a preferred embodiment of the present invention.